This invention relates to a method of, and apparatus for, feeding a continuous web of paper or like material into a rotary press or other machine. More specifically the invention concerns such a method and apparatus featuring the automatic splicing of successive rolls of web without the need for suspending the feeding of the web into the rotary press or the like.
Although the method and apparatus of this invention have particular utility in conjunction with web-fed rotary presses, they lend themselves to use with a web coater, corrugator, or any other machine which either consumes or processes continuous webs. Thus, hereinafter in this specification and in the claims appended thereto, all such machines to which the invention finds applications will be generally referred to as "web consuming or processing machines". Further the terms "old web" and "old web roll" will be used herein and in the claims appended hereto to mean the web and roll, respectively, that have been being consumed or processed. The terms "new web" and "new web roll" signify the fresh web and roll, respectively, that are to be, or being, spliced to the old web or roll.
Two methods have been known for splicing successvie rolls of web without suspending the feeding of the web into the consuming or processing machine. One is called the "zero speed method", such that the old and new rolls of web are both held out of rotation during splicing. The other is the "speed matching method" wherein the new web roll is revolved at a peripheral speed equal to the running speed of the old web for splicing them at zero relative speed. A more extensive discussion of these prior art splicing methods follows.
U.S. Pat. No. 4,233,104 describes and claims apparatus constructed to carry the zero speed method into practice. The apparatus broadly comprises an infeed mechanism for feeding a web into a consuming or processing machine, a splicer mechanism incorporated with the infeed mechanism for splicing successive rolls of the web, and a web storage mechanism interposed between the infeed mechanism and the consuming or processing machine for holding a required length of the web for delivery to the consuming or processing machine during the splicing of successive web rolls.
The infeed mechanism has a pair of roll holder arms medially pivoted for joint rotation. The roll holder arms carry old and new web rolls on their opposite ends, and the splicer mechanism therebetween. The splicer mechanism includes a pair of nip rolls movable toward and away from each other and having suction ports created therein. Upon decrease of its radius to a prescribed degree the old web becomes locked against rotation to discontinue the payoff of the web therefrom and hence to allow this web to be spliced to the new web. During the subsequent splicing operation the web storage mechanism operates to feed the web length that has been stored therein into the consuming or processing machine.
The new web roll has attached to its leading end a piece of tape having adhesive layers on its opposite faces. This taped end of the new web is held by suction against one of the nip rolls of the splicer mechanism. The old web is wrapped around the other nip roll on its way toward the web storage mechanism. The old and new webs can therefore be joined together via the adhesive tape by pressing the nip rolls against each other. The old web is cut off from its roll by a knife positioned adjacent the nip rolls. Then the infeed mechanism resumes the feeding of the web from the new roll.
The speed matching method, on the other hand, also dictates the use of an infeed mechanism comprising a pair of rotatable roll holder arms, but of no web storage mechanism. The roll holder arms rotatably carry old and new web rolls on their opposite ends. During normal feeding operation the roll holder arms extend approximately vertically, with the old web roll held above and the new web roll below. Upon decrease in the radius of the old web roll to a predetermined degree the roll holder arms are turned approximately 180 degrees, so that the new web roll comes above and the old one comes below.
Disposed above the roll holder arms is a speed matching mechanism including a drive roll which is movable into and out of peripheral contact with the new web roll. At the time of splicing, the drive roll revolves the new web roll about its own axis at a peripheral speed equal to the running speed of the old web traveling therepast.
Also disposed adjacent the roll holder arms is a retractable splicer mechanism which, when in its working position, guides the old web thereover so as to pass substantially tangentially of the new web roll. As the peripheral speed of the new web roll becomes equal to the running speed of the old web as above, the splicer mechanism presses, with a brush incorporated therein, the old web against an adhesive region at the leading end of the new web. Then the old web is severed from its roll by a knife disposed adjacent the splicer brush. Thus the infeed mechanism commences the payoff of the web from the new roll whereas the splicer mechanism returns to its retracted position.
The zero speed and speed matching schemes, as practiced heretofore, have their own drawbacks. In the apparatus built on the zero speed scheme the old and new webs are joined together by the pair of nip rolls spaced from their rolls. This requires the manual threading of the leading end of each new web, with an adhesive tape attached thereto, between the nip rolls, thus making difficult the full automation of the apparatus. The adhesive tape, moreover, must be attached to the new web roll on the splicer mechanism; it cannot be applied to new web rolls preparatory to their mounting on the apparatus.
The apparatus embodying the speed matching scheme, on the other hand, requires the expensive speed matching mechanism for precisely synchronizing the peripheral speed of the new web roll with the running speed of the old web. The speed matching method is also more difficult to practice than the zero speed method. The successive web rolls are likely to be spliced improperly, or not spliced at all, if the leading end of the new web roll comes off during the rotation of the roll or if its peripheral speed does not equal to the running speed of the old web by reason of, for example, the eccentricity of the new web roll. Further the old web has a considerable length of its portion trailing behind the region where it is adhered to the new web. The length of this trailing end portion should be reduced to a minimum so as not to interfere with the operation of the web consuming or processing machine. It is also a disadvantage of the speed matching method that the adhesive region or regions on the leading end of each new web must be of very complex pattern in order to afford a firm bond to the old web, since the webs are spliced while running. The preparation of such complex adhesive regions is of course a troublesome and time consuming job which is difficult of automation.
The prior art web feeders built on both the zero speed and the speed matching schemes have an additional problem in common with regard to the alignment of the successive web rolls. The aforesaid pair of roll holder arms have two pairs of opposed chucking cones on their opposite ends for engagement in the respective hollow cores of the old and new web rolls.
No alignment problem would occur if all the web rolls had their webs rolled in the same axial position on the hollow cores. Actually, however, some axial displacement of the webs on the cores is usual. Should these web rolls be spliced with the axial displacement of the webs uncorrected, the successive lengths of the web would have corresponding lateral displacement. Let us consider the case where the web is fed into an offset printing press. Passing between the blanket cylinders of the press, the laterally displaced length of the web would be caught between the ink piles of the cylinders and so might partly be cut off, or at least the image would be printed out of place on the web.
Conventionally, therefore, it has been the duty of a pressman to visually examine the axial position of each new web roll on its core and, as required, to manually shift the web roll axially on the core. The manual labor, of course, runs counter to the desired higher production of the press.
A still further problem with the prior art concerns the means for preventing the end of each web roll from coming off the roll. Taping is the usual expedient to this end. The web end, however, must readily come off the roll when spliced to the old web. The conventional practice has been to apply relatively wide, strong tape to each web roll to prevent the loosening of its end during transportation and handling. The strong tape is peeled off the web roll just before its use, and narrower, easier-to-break tape is applied in several spaced apart positions across the web end. However, the narrower tape as heretofore used has been too weak to hold the web end against the roll and has been easy to break during the handling of the roll as for mounting the same on the pair of roll holder arms.